GRAVISTATIC HEAT 291 



ing a dumb-bell and directly letting it drop to the ground, 

 and confining the attention to this simple case. It is ex- 

 plained, that in elevating the bell the lifter expends pre- 

 cisely the same number of units of muscular energy which 

 the bell will develop in thermal units on being let go and 

 striking the ground. "Muscular units expended, are 

 compensated by positional units gained, and positional 

 units lost, in their turn, are compensated by thermal 

 units gained; and so on." But suppose the bell is too 

 heavy for you to so much as budge? 



Ah, that is a question which you are supposed to be 

 polite enough never to ask. It seems as plain as can be 

 that when you lift the dumb-bell, you use up a certain 

 amount of muscular energy ; but it seems just as evident, 

 too, does it not, that when you pull and pull on an iron 

 stanchion, or try to lift a heavy rail, without effecting 

 the slightest movement in either, you are quite as cer- 

 tainly expending muscular energy! In the case of the 

 dumb-bell our good friends tell us these units of muscular 

 energy are replaced in the shape of kinetic energy by the 

 fall of the bell, thus balancing the dynamical ledger ; but 

 they do not volunteer as to how they are compensated in 

 the second instance. 



Doubtless you have seen a team of horses straining 

 to overcome a rise in the road and being lashed merci- 

 lessly by a brutal driver. Ten minutes pass, perhaps, 

 with no progress made, and the mired wheels stick fast. 

 Had all gone well and the hill been surmounted, we should 

 be told the old fable of energy compensations ; but not so 

 in this case. These Conservationists know when ignor- 

 ance is bliss, silence golden, and discretion the better 

 part of valor. Possibly, too, you may have seen a horse 

 bending every effort to hoist a trio of bales tied to a pul- 

 ley; half way up something goes wrong, the horse pulls 

 as hard as ever, but the load refuses to rise. What sus- 

 tains the load thus in mid-air? Cut the traces and you 

 will see that it is the pull of the animal. In fine, these 

 examples demonstrate that energy is often expended, 

 lost, destroyed in merely maintaining, or not altering, 

 the status. 



